Published online Nov 27, 2020. doi: 10.4254/wjh.v12.i11.965
Peer-review started: July 16, 2020
First decision: September 14, 2020
Revised: September 16, 2020
Accepted: October 5, 2020
Article in press: October 5, 2020
Published online: November 27, 2020
The morbidity and mortality of human immunodeficiency virus (HIV)-infection is often associated with liver disease, which progresses slowly into severe liver dysfunction. There are multiple insults which exacerbate HIV-related liver injury, including HIV-associated dysregulation of lipid metabolism and fat turnover, co-infections with hepatotropic viruses and alcohol abuse. As we reported before, exposure of hepatocytes to HIV and alcohol metabolites causes high oxidative stress, impairs proteasomal and lysosomal functions leading to accumulation of HIV in these cells, which end-ups with apoptotic cell death and finally promotes development of liver fibrosis.
To study whether obeticholic acid (OCA) prevents HIV/ethanol metabolism-induced hepatotoxicity and subsequent activation of hepatic stellate cells (HSC) by HIV+ apoptotic hepatocyte engulfment.
Huh7.5-CYP (RLW) cells were exposed to HIV and acetaldehyde-generating system (AGS) in the presence or absence of OCA. In the cells, we measured the expression of HIV-related markers: HIVgagRNA-by real-time polymerase chain reaction (PCR), p24- by western blot, HIV DNA-by semi-nested PCR, integrated HIV DNA-by ddPCR. Lysosomal and proteasomal activities were measured using fluorometrically-labeled substrates. For hepatocyte apoptosis, cleaved caspase 3 and cleaved PARP were visualized by western blot and cytokeratin 18- by M30 ELISA-in supernatants. Apoptotic bodies were generated from untreated and HIV-treated RLW cells exposed to UV light. Pro-fibrotic activation of HSC was characterized by Col1A1 and transforming growth factor-β mRNAs, while inflammasome activation- by NLRP3, caspase 1, interleukin (IL)-6, IL-1β mRNA levels.
In RLW cells, OCA treatment attenuated HIV-AGS-induced accumulation of HIVgagRNA, HIV DNA and p24. OCA suppressed reactive oxygen species production and restored chymotrypsin-like proteasome activity as well as cathepsin B lysosome activity. OCA also decreased HIV-AGS-triggered apoptosis in RLW cells. Exposure of HIV-containing apoptotic hepatocytes to HSC prevented activation of inflammasome and induced pro-fibrotic activation in these cells.
We conclude that by suppressing oxidative stress and restoring proteasomal and lysosomal functions impaired by HIV and ethanol metabolism, OCA decreases accumulation of HIV in hepatocytes, leading to down-regulation of apoptosis in these cells. In addition, OCA reverses pro-fibrotic and inflammasome-related activation of HSC triggered by engulfment of HIV-containing apoptotic hepatocytes, potentially contributing to suppression of liver fibrosis development.
Core Tip: We investigated the ability of obeticholic acid (OCA) to reverse pro-fibrotic effects of human immunodeficiency virus (HIV) and ethanol metabolism in liver cells. Based on our previous studies, hepatocyte apoptosis occurs under combined exposure of cells to HIV and ethanol metabolites. The subsequent engulfment of HIV-containing apoptotic hepatocytes by hepatic stellate cells induced pro-fibrotic activation in these cells, thereby promoting fibrosis development. Here, we demonstrated that OCA attenuates hepatocyte apoptosis by preventing accumulation of HIV components in liver cells exposed to virus and acetaldehyde-generating system (AGS) mimicking natural ethanol metabolism in primary hepatocytes. These beneficial effects of OCA are attributed to suppression of oxidative stress leading to restoration of HIV-AGS-impaired proteasomal and lysosomal functions in liver cells. OCA also reduces activation of inflammasome in hepatic stellate cells and their pro-fibrotic activation. Thus, anti-fibrotic properties of OCA can be used for combined treatment of HIV-infected alcohol abusers with a high risk of liver fibrosis development.